11. Insect management

OBJECTIVE: Determine pest management action levels for insect populations.

Use existing insect action level guidelines as a starting point for a specific site. 

• Site-specific action levels vary based on desired quality and use of the turf, pest potential, quality of monitoring, and history of the site. 

  Table 18. Approximate threshold guidelines for turfgrass insect pests.

  insect	Approximate threshold per sq. ft.
  Japanese beetle	8 - 15 larvae
  Oriental beetle	8 - 15 larvae
  Masked chafer	6 - 15 larvae
  European chafer	3 - 8 larvae
  Asiatic garden beetle	12 - 20 larvae
  May beetle (phyllophaga)	2 - 4 larvae
  Black turfgrass ataenius	15 - 80 larvae
  Annual bluegrass weevil	10 - 80 larvae
  Bluegrass billbug	No good estimate available
  Chinch bug	30 - 50 nymphs
  Sod webworm, cutworm	No good estimate available

• Use guidelines for action levels for insects as general starting points only.   
  • Example: some turf areas may lose turf cover or be subject to damage from grub-foraging animals such as skunks with 4 or 5 grubs per square foot, while others (with available irrigation, higher mowing heights, low traffic) may sustain populations of 25 to 30 grubs per square foot with no apparent damage. 
• Keep records diligently to keep track of ‘hot spots’ and also for predicting future activity.
  • Example: a record beetle flight in early summer may be an indicator of the potential for damaging populations of grubs later in the summer and into the fall and the following spring.

OBJECTIVE: Establish and conduct a scouting program for insects. 

Monitor regularly for insects to inform management decisions. 

• Management decisions are often aided by visual scouting. 
• Appropriate scouting techniques should be used for particular insect(s). Counts of insects per unit area are helpful in estimating overall populations. 
• Record observations on a site map or to a list with the location identified.   
• Note particular ‘hot spots’ or areas of early insect activity that might act as indicator points for future seasons. 

* Refer to the table, ‘Insect sampling techniques’ below.

** Use pheromone traps with care. They are useful for determining when beetle adults begin to fly, but can also potentially attract more damaging insects into an area.

Use appropriate techniques for effective insect scouting. 

• Proper scouting techniques vary depending upon the target insect species. 
• Correct scouting techniques are designed to effectively gauge the level of insect populations while minimizing turf disturbance. 

OBJECTIVE: Use proper cultural practices designed to prevent insect populations from reaching damaging levels. 

Reduce environmental stress and maintain plant vigor. 

• Supply adequate and balanced nutrition through the fertility program to yield a dense and well-rooted turf.  
• Time and deliver irrigation so as to prevent moisture stress. 
• Manage excessive thatch by adjusting fertility levels, mechanical removal or other means. 
• Set height of cut at maximum acceptable height.  

Keep up with needed repairs. 

• Overseed with desired turfgrasses in late summer-early fall if turf has thinned due to drought dormancy or insect infestation. 
• When turf has been dislodged by animals and birds seeking grubs, replace and roll to bring roots back into contact with soil. 
• Use high quality sod free of turf damaging insects during renovation and establishment. 

Plant endophytic cultivars whenever possible. 

• At present there are some endophytic cultivars of perennial ryegrass, tall fescue, hard fescue and Chewings fescue available. 
• Endophytic cultivars have a beneficial fungus called an endophyte within the seed and above-ground portions of the plant itself. 
• Endophyte-enhanced cultivars tend to be vigorous even under conditions of stress, and exhibit a level of resistance to foliar feeding insects such as sod webworms, and in particular chinchbugs and billbugs. 
• Endophytes impart no tolerance or resistance to root feeding insects such as white grubs. 
• Endophytic turfgrass cultivars should not be used where animals may graze. 

Encourage beneficial insects. 

• The role of beneficial insects is crucial to thatch management, and to the overall health of the turf. 
• Some beneficial insects, such as big-eyed bugs, are predators that may feed on eggs and larvae of turf-damaging insects. 
• Unfortunately, some of the insecticides that are currently used in turf settings are ‘broad spectrum’ materials; this means they kill a wide range of insects, including many beneficial insects. 
• Insecticide applications should be made only when sampling has demonstrated that a pest population has reached the threshold level, and only to areas for which infestation has been confirmed through careful monitoring. 

OBJECTIVE: Use insecticides intelligently when other means fail to acceptably control insect pest(s) present. 

Discourage insecticide resistance. 

• Rotate insecticide chemical classes as appropriate. 
• For ease of reference, Insecticide Resistance Action Committee (IRAC) codes are available to aid in insecticide resistance management. Refer to UMass Extension’s 2010-2011 Professional Guide for IPM in Turf for Massachusetts or  http://www.irac-online.org. 

Consider pesticide characteristics when selecting an insecticide. 

• Some insecticides have curative effect, while others are designed to be preventive materials. 
• Some turf insecticides act very quickly while others take much longer to kill the target insect. 
• In addition, some materials persist for several weeks and remain active, while others break down in a matter of a few days. 

Give particular consideration to potential human and environmental impacts when applying insecticides. 

• Understand the mobility and persistence of the material intended for use. 
• Many materials are toxic to fish, aquatic invertebrates, and/or foraging bees. This information can be found under ‘Environmental Considerations’ on the pesticide label. 
• Do not apply insecticides harmful to foraging bees to lawns in which white clover is in bloom. 
• Use proper personal protective equipment (PPE) for mixing and application activities. 
• Observe specified re-entry intervals. 

Take steps to insure insecticide efficacy. 

• Use insecticides only when insect presence has been documented and those insects are in a susceptible stage. 
• Many pesticide materials need to be ‘watered-in’. Irrigate according to label directions before and/or after insecticide applications. This is especially important for soil dwelling insects. 
• Test spray water source(s) regularly for pH. 
• Consult the label for the appropriate temperature range for application. Some insecticides are less effective at lower temperatures, while others can damage turf when applied in hot weather. 

Apply preventive insecticides responsibly. 

• Preventive materials are applied before a noticeable pest population develops, and are therefore not based on a current population exceeding a set action threshold. 
• If scouting the previous year confirmed the presence of damaging populations, a preventive insecticide may be justified. 
• Preventive insecticide should be used in conjunction with proper cultural practices that provide the best agronomic conditions for turf health.